Alpine-touring (AT) ski bindings offer the versatility of skiing in “downhill” (fixed heel) or “touring” (free heel) modes. AT skiing has been enjoyed in Europe for decades, where it was known originally as randonnee skiing, but only more recently has it gained popularity in the United States.
Conventional AT bindings function in two ways. For touring in free heel mode, a rear locking clasp is opened, allowing the heel to lift free of the ski, so that the heel can pivot with respect to the ball of the foot or the toe. A free heel is preferable for a natural striding motion, for kick and gliding in the snowy backcountry, or for climbing slopes on skis. On a downhill, the heel clasp is optionally locked down to secure the heel, allowing the skier to aggressively apply more power through the binding for turning and carving with the ski edges (as with conventional alpine bindings), and provides more support for protection of the knees and ankles.
Although the earliest AT bindings, such as the Silvretta Saas Fee, had a pivotable toe and a heel support, a plate or frame supporting the bootsole soon gained preference. An early representation of an AT binding is described by Hollenback (U.S. Pat. No. 3,388,918). As shown in FIG. 1, the binding includes a frame member (1) pivotably attached to the ski blade (2) at the toe and a releasable butterfly nut (3) for restraining the frame member at the heel when desired. Also shown are heel and toe restraints for holding the boot.
McGowan in expired U.S. Pat. No. 5,560,633 provides for a scissors device with frame that hinges at the toe on a mounting bar, which in turn reversibly clips into conventional ski binding toe and heel members on the ski. The pivotable frame is extensible with adjustment for boot size and includes bails for securing a boot. Engageable climbing bars are affixed to the lower mounting bar of the scissors frame. The device has been well received because it can be clipped into any alpine ski binding without tools, affording crossover flexibility but at the expense of substantially increased weight. The torque of a fall will not reliably release the device from the ski, which can result in injury, and the boot is necessarily elevated to accommodate the raised mounting bar. It is thought that building an adaptor plate without these problems would add great weight and expense.
Ramer, in U.S. Pat. No. 4,674,766 shows a simple clasp for securing an extensible plate at the heel. In U.S. Pat. No. 5,328,320, also to Ramer, the clasp (5) is modified to reversibly engage a tab (6) projecting from the heel plate (4) and rotates up and away to release the heel plate, as shown here in FIG. 2. The rotatable clasp is secured in a locked position by a spring-loaded cam. The clasp is further modified to include a pair of risers (7,8) for supporting the heel at one of two angles above the ski. However, the clasp does not accommodate flexing of the ski under the binding, which can damage the ski blade (2) or the binding and leads to loss of camber with use, particularly with soft-flexing skis that have a wide tip and a very narrow waist.
Fritschi, in U.S. Pat. No. 5,735,541 describes a hollow tubular carrier beam hingedly secured at the toe to a ski, with a heel binding jaw member slideably mounted on the beam for securing the boot against the toe release anvil. A locking member engages the rear endcap of the beam and locks down the heel when flat, and serves as a riser when standing. Unfortunately however, bowing of the ski can release the locking member from the endcap, resulting in unwanted detachment of the heel on one or both skis. And because the skier's boot rides on toe and heel platforms above the carrier beam, the skier is elevated above the ski by an undesirable height for some riding styles.
More generally, rotational and torsional forces on the carrier beam tend to focus on the toe pivot cradle and axial pin, leading to undesirable lateral play and looseness over time with use, which can necessitate replacement of the entire binding assembly. It would be preferable for a binding to be supplied with a toe pivot cradle independent of the toe release so that it is easily replaced, and which spreads the loads on the toe cradle so as to reduce wear and fatigue.
In the interests preventing broken bones and torn knees, conventional toe and heel bindings are supplied with break-away releases that detach when torsional forces on the boot exceed safe limits. Industry standards have been developed for performance and testing of release mechanisms. Because conventional AT bindings are built with a hinge at the toe, the toe release mechanism is not as strong as alpine ski bindings. Thus the durability of AT bindings known in the art is not trusted for aggressive skiing and under harder or variable snow conditions, and a skier wishing both types of skiing will likely have two pairs of skis, one of which is fitted with the AT ski bindings, the other with the alpine ski bindings—at additional expense and inconvenience.
As currently practiced, it is not possible to conveniently exchange or swap out bindings from ski to ski. In contrast, the AT ski binding adaptor of the present invention permits the skier to readily move bindings from ski to ski. The inventive AT ski binding adaptor is supplied with a reversible heel lock for crossover flexibility between fixed heel and free heel modes. The floating heel lock mechanism accommodates the flexing of the skis under a variety of ski conditions and terrain favored by modern skiers. In a preferred embodiment, the ski binding adaptor is compatible with multiple ski bindings, and is thus a “universal” adaptor mounting plate. Other advantages will be apparent from the following drawings and description.